1. Field of the Invention
The present invention relates generally to a pattern information processing method and an apparatus for carrying out the above method.
2. Description of the Prior Art
In the art of inspecting objects there have been proposed various kinds of pattern information processing methods and apparatus. According to the prior art methods, the pattern information of an object to be inspected or recognized is converted into two values of black and white as data representing the shape, area and so on of the object and this data is compared with the data of a reference body which is preliminarily set to judge whether the object is good or not.
In fact, however, such practical objects, which can be divided into two values of black and white clearly, are few. In general, objects have a certain degree of light and shade in addition to black and white. Therefore, the prior art method is not satisfactory to inspect an object which has a complicated pattern.
In the case where the prior art pattern information processing method uses a television camera or the like, its picture screen is divided into, for example, 500.times.500 picture elements, the degree of light and darkness of an image projected onto each of the picture elements is converted by an A/D (analog to digital) converter into a digital value as data, and this data is processed by a computer or the like to extract the features of the object which is picked up by the television camera. In such case, the amount of the data becomes massive and much time is required to process such massive amount of data. There also are methods of inspecting for flaws or the like of an article, whereby the picture screen of a television camera is not divided into a plurality of picture elements but a certain value of threhold level is set, and then as an example only the part of the video signal from the television camera, which video signal that exceeds the threshold value, is converted into two values, and the values are counted to represent the feature of the object or to detect a flaw of the object.
The above prior art method will be described with reference to FIG. 1. In this case, a single threshold value S1 is set and the inspection of an object is conducted by judgement of whether or not a video signal S2 from a television camera which picks up the object to be inspected exceeds the threshold value S1. This method is effective for inspecting objects or flaws which are simple in pattern but are not suitable to inspect objects with complicated patterns.